<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .app {
            /* width: 100%; */
            /* height: 100%; */
        }
        .app .block{
            width: 500px;
            height: 340px;
            overflow: hidden;
            border: 1px solid rgb(70, 14, 121);
            position: relative;
            margin-bottom: 10px;
        }
        .app .con{
            width: 500px;
            height: 340px;
            margin: 0 auto;
            position: absolute;
            top: 0;
            /* overflow: auto; */
            background-color: aquamarine;
        }
        .app .item{
            width: 100%;
            height: 100px;
            border: 1px;
            margin-bottom: 10px;
            background-color: red;
        }
        .mt-20{
            margin-top: 20px;
        }
    </style>
</head>
<body>
    <h1>div margin 测试</h1>
    <div class="app">
       <div class="block">
         <div class="con">
            <div class="item mt-20">1</div>
            <div class="item mt-20">2</div>
            <div class="item mt-20">3</div>
        </div>
       </div>
         <div class="block">
             <div class="con">
            <div class="item mt-20">11</div>
            <div class="item mt-20">22</div>
            <div class="item mt-20">33</div>
        </div>
         </div>
    </div>
</body>
</html>